George Gunn wrote in response to Jonathan Robie's question:
"See the excellent treatment of this passage in Peter Cotterell & Max Turner,
linguistics & Biblical Interpretation (IVP, 1989) pp. 302-307. The proverb
is evidently an Egyptian proverb that found its way into Proverbs (25:1,2)."

Since this work may be difficult to access for some readers including
myself, it would be very helpful for George to give us, if he doesn't mind,
a brief explanation of the idiom "heaping coals of fire". Thanks,
Johnny Felker